1. Field of the Invention
The present invention relates to a method of manufacturing a multilayer ceramic component including a capacitor, and more particularly, it relates to a process for a multilayer ceramic component including capacitor which enables acquisition of a desired electrostatic capacitance in high accuracy.
2. Description of the Background Art
In general, a multilayer ceramic capacitor is prepared through the following steps:
First, a ceramic green sheet is molded from a ceramic slurry. Then, conductive paste is applied onto the ceramic green sheet by a method such as screen printing, for forming an internal electrode. Then, a plurality of such ceramic green sheets provided with internal electrodes are stacked with each other and pressurized along the direction of thickness, to obtain a laminate. Then, the obtained laminate is fired to provide a ceramic sintered body, and thereafter external electrodes are formed on both end surfaces of the sintered body. FIG. 6 shows an exemplary multilayer capacitor 30 obtained in this manner.
As clearly understood from FIG. 6, a plurality of internal electrodes 32a to 32g are arranged in the multilayer ceramic capacitor 30 to overlap with each other through sintered body layers. The electrostatic capacitance of the multilayer ceramic capacitor 30 is decided by the thicknesses of the sintered body layers which are held between the internal electrodes 32a to 32g, overlapping areas of the internal electrodes 32a to 32g which are opposed to each other through the sintered body layers, and the dielectric constant of dielectric ceramics forming the sintered body layers.
In general, the sintered body layers which are held between the internal electrodes 32a to 32g have considerably small thicknesses of 5 .mu.m to 50 .mu.m. In the aforementioned method, therefore, slight fluctuation of the thicknesses of the ceramic green sheets results in remarkable fluctuation of the electrostatic capacitance. In order to implement a desired electrostatic capacitance in the multilayer ceramic capacitor, therefore, it is necessary to control the thicknesses of the employed ceramic green sheets in high accuracy.
In actual preparation of the multilayer ceramic capacitor, on the other hand, conductive patterns for forming the internal electrodes are provided on a mother green sheet, thereafter the mother ceramic green sheet which is provided with the conductive patterns is punched out into prescribed dimensions, and a plurality of the punched ceramic green sheets are stacked with each other to obtain a mother laminate, for improving mass productivity. Thereafter the mother laminate is cut along its thickness, thereby obtaining laminates for respective multilayer ceramic capacitors.
In general, the aforementioned ceramic green sheet is molded to have an elongated shape by a doctor blade coater or a roll coater method. In such a long ceramic green sheet molded in the aforementioned method, however, the thickness tends to disperse depending on the molding speed or the viscosity of the employed ceramic slurry, and partial dispersion of the thickness is not negligible.
When a multilayer ceramic capacitor is prepared in accordance with the conventional method, therefore, it is impossible to avoid dispersion of the electrostatic capacitance in the obtained ceramic green sheets. In order to prevent such dispersion of the electrostatic capacitance, therefore, the following method is employed in general:
After ceramic green sheets provided with internal electrodes for forming the electrostatic capacitance are stacked with each other, an additional ceramic green sheet for adjusting the electrostatic capacitance is further stacked on the laminate in consideration of the dispersion of the electrostatic capacitance which may be caused in the laminate, thereby implementing the necessary electrostatic capacitance.
In such a method of further stacking the additional ceramic green sheet provided with the electrode for adjusting the electrostatic capacitance, however, the preparation steps are complicated since the additional ceramic green sheet provided with an electrode for adjusting the electrostatic capacitance must be prepared, i.e., an electrode pattern for adjusting the electrostatic capacitance is required in addition to electrode patterns forming the internal electrodes.
In addition, the thicknesses of the ceramic green sheets may be considerably changed with time to result in thickness fluctuation of several .mu.m. When a certain degree of time is required in advance of stacking after molding of the ceramic green sheets, therefore, it is necessary to change the laminate structure in response to the fluctuation of the thicknesses of the ceramic green sheets, in order to implement the target electrostatic capacitance. Thus, the method of forming the electrode pattern for adjusting the electrostatic capacitance still tends to cause an error between designed and actual electrostatic capacitances.